/* -*- P4_16 -*- */
#include <core.p4>
#include <v1model.p4>

const bit<16> ETH_TYPE_IPV4 = 0x800;  // IPv4 Ethernet type

/*************************************************************************
*********************** H E A D E R S  ***********************************
*************************************************************************/

typedef bit<9>  egressSpec_t;    // Egress port specification
typedef bit<48> macAddr_t;       // MAC address type
typedef bit<32> ip4Addr_t;       // IPv4 address type

header ethernet_hdr {
    macAddr_t dstAddr;
    macAddr_t srcAddr;
    bit<16>   etherType;
}

header ipv4_hdr {
    bit<4>    version;        // IP version (4 bits)
    bit<4>    ihl;            // Internet Header Length
    bit<8>    diffserv;       // Differentiated Services
    bit<16>   totalLen;       // Total length
    bit<16>   identification; // Identification
    bit<3>    flags;          // Flags
    bit<13>   fragOffset;     // Fragment offset
    bit<8>    ttl;            // Time to live
    bit<8>    protocol;       // Protocol (6=TCP, 17=UDP)
    bit<16>   hdrChecksum;    // Header checksum
    ip4Addr_t srcAddr;        // Source IP
    ip4Addr_t dstAddr;        // Destination IP
}

header tcp_hdr {
    bit<16> srcPort;     // Source port
    bit<16> dstPort;     // Destination port
    bit<32> seqNo;       // Sequence number
    bit<32> ackNo;       // Acknowledgment number
    bit<4>  dataOffset;  // Data offset
    bit<3>  res;         // Reserved
    bit<3>  ecn;         // ECN flags
    bit<6>  ctrl;        // Control bits
    bit<16> window;      // Window size
    bit<16> checksum;    // Checksum
    bit<16> urgentPtr;   // Urgent pointer
}

header udp_hdr {
    bit<16> srcPort;     // Source port
    bit<16> dstPort;     // Destination port
    bit<16> pkt_length;  // Packet length
    bit<16> checksum;    // Checksum
}

struct metadata {
    /* Empty metadata structure */
}

struct headers {
    ethernet_hdr   ethernet;
    ipv4_hdr       ipv4;
    tcp_hdr        tcp;
    udp_hdr        udp;
}

/*************************************************************************
*********************** P A R S E R  ***********************************
*************************************************************************/

parser MyParser(packet_in packet,
                out headers hdr,
                inout metadata meta,
                inout standard_metadata_t standard_metadata) {

    state start {
        transition parse_ethernet;
    }

    state parse_ethernet {
        packet.extract(hdr.ethernet);
        transition select(hdr.ethernet.etherType) {
            ETH_TYPE_IPV4: parse_ipv4;
            default: accept;
        }
    }

    state parse_ipv4 {
        packet.extract(hdr.ipv4);
        transition select(hdr.ipv4.protocol) {
            6: parse_tcp;    // TCP protocol
            17: parse_udp;   // UDP protocol
            default: accept;
        }
    }

    state parse_tcp {
        packet.extract(hdr.tcp);
        transition accept;
    }

    state parse_udp {
        packet.extract(hdr.udp);
        transition accept;
    }

}

/*************************************************************************
************   C H E C K S U M    V E R I F I C A T I O N   *************
*************************************************************************/

control MyVerifyChecksum(inout headers hdr, inout metadata meta) {
    apply {  }
}

/*************************************************************************
**************  I N G R E S S   P R O C E S S I N G   *******************
*************************************************************************/

control MyIngress(inout headers hdr,
                  inout metadata meta,
                  inout standard_metadata_t standard_metadata) {

    action drop_packet() {
        mark_to_drop(standard_metadata);
    }

    action ipv4_forward(macAddr_t dstAddr, egressSpec_t port) {
        standard_metadata.egress_spec = port;
        hdr.ethernet.srcAddr = hdr.ethernet.dstAddr;
        hdr.ethernet.dstAddr = dstAddr;
        hdr.ipv4.ttl = hdr.ipv4.ttl - 1;
    }

    table ipv4_lpm {
        key = {
            hdr.ipv4.dstAddr: lpm;  // Longest prefix match
        }
        actions = {
            ipv4_forward;
            drop_packet;
            NoAction;
        }
        size = 1024;
        default_action = drop_packet();
    }

    table acl_ip_t {
        key = {
            hdr.ipv4.dstAddr: ternary;  // Ternary match
        }
        actions = {
            drop_packet;
            NoAction;
        }
        size = 1024;
        default_action = NoAction();
    }

    table acl_udp_t {
        key = {
            hdr.udp.dstPort: ternary;  // Ternary match
        }
        actions = {
            drop_packet;
            NoAction;
        }
        size = 1024;
        default_action = NoAction();
    }

    apply {
        if (hdr.ipv4.isValid()) {
            ipv4_lpm.apply();
            acl_ip_t.apply();
            if (hdr.udp.isValid()) {
                acl_udp_t.apply();
            }
        }
    }
}

/*************************************************************************
****************  E G R E S S   P R O C E S S I N G   *******************
*************************************************************************/

control MyEgress(inout headers hdr,
                 inout metadata meta,
                 inout standard_metadata_t standard_metadata) {
    apply {  }
}

/*************************************************************************
*************   C H E C K S U M    C O M P U T A T I O N   **************
*************************************************************************/

control MyComputeChecksum(inout headers  hdr, inout metadata meta) {
     apply {
	update_checksum(
	    hdr.ipv4.isValid(),
            { hdr.ipv4.version,
	      hdr.ipv4.ihl,
              hdr.ipv4.diffserv,
              hdr.ipv4.totalLen,
              hdr.ipv4.identification,
              hdr.ipv4.flags,
              hdr.ipv4.fragOffset,
              hdr.ipv4.ttl,
              hdr.ipv4.protocol,
              hdr.ipv4.srcAddr,
              hdr.ipv4.dstAddr },
            hdr.ipv4.hdrChecksum,
            HashAlgorithm.csum16);
    }
}

/*************************************************************************
***********************  D E P A R S E R  *******************************
*************************************************************************/

control MyDeparser(packet_out packet, in headers hdr) {
    apply {
        packet.emit(hdr.ethernet);
        packet.emit(hdr.ipv4);
        packet.emit(hdr.tcp);
        packet.emit(hdr.udp);
    }
}

/*************************************************************************
***********************  S W I T C H  *******************************
*************************************************************************/

V1Switch(
MyParser(),
MyVerifyChecksum(),
MyIngress(),
MyEgress(),
MyComputeChecksum(),
MyDeparser()
) main;